Two component polyurethane adhesives are known and have been widely used in bonding structural components. In practice, a first component which includes an isocyanate prepolymer is mixed with a curative, polyhydroxyl component and suitable catalysts and other functional agents.
A sag resistant, two component polyurethane adhesive has been disclosed in U.S. Pat. No. 4,743,672. The adhesive thus disclosed comprise an isocyanate prepolymer and as a second component a mixture of polyol, a poly(alkylene) oxide polyamine and a catalyst, the aromatic amine terminated polyether of the present invention is not at all disclosed. Also noted is U.S. Pat. No. 4,595,445 which disclosed an adhesive composition comprising a polyisocyanate of retarded reactivity and a polyamine.
U.S. Pat. Nos. 3,979,364, 4,336,298, 4,444,976 and 4,552,934 and European Pat. No. 63,534 all relate to the use of amines in making non-sagging adhesives.
In U.S. Pat. No. 3,714,127, there is disclosed the addition of a diamine to a two component polyurethane based adhesive for the purpose of increasing the viscosity of the adhesive to eliminate run-off or dripping.
It is an object of the invention to develop a two component polyurethane structural adhesive which is suitable for bonding relatively thin and or elastic and or soft sheets classified as class A surfaces.
It is a further object of the invention to develop an adhesive which is suitable for high volume bonding applications which is characterized in that the viscosity of each of its components is less than 15,000 cps.